Power unit



June 1, 1954 s. B.' MCLEOD 2,680,016

POWER UNIT Filed Deo. I5, 1950 2 Sheets-Sheet 1 STEW RT .MCLEOD -By MM '|24 W 75 ATTORN YS June l, 1954 s. B. MCLEOD I 2,680,016

POWER UNIT Filed Dec. l5. 1950 2 Sheets-Sheet 2 r l 4 I V seN 28" los 54/ l 72 s4 1o X 1 u2 76 24... H I

63, L: l jf- 8 5o I m 'O2 INVENTOR.

STEWART B MCLEOD ATTORN YS Patented June l, 1954 man STATES ATENT oFFlcE 29 Claims.

r1`he present invention relates to a power unit and more particularly, to a combination electric motor, hydraulic pump, and hydraulic device combined into a compact self-contained unit.

It is an object of the present invention to provide a power unit of the character described, particularly adapted to serve as an actuator for raising and lowering windows in a vehicle.

It is a further object of the present invention to provide a self -contained electric-hydraulic power unit designed to be self-locking in one di rection so as to prevent opening of the window by the application of mechanical force when the pump is not operating, while permitting manual reverse movement.

It is a further object of the present invention to provide an electric-hydraulic power unit including a pump, a piston and cylinder device arranged to have differential uid inflow and outflow during operation, a iluid reservoir adapted to receive excess flow of uid or to furnish fluid as required in the operation of the device, check valves controlling flow of fluid into said reservoir, a by-pass around the motor, and means effective to close both check valves upon the application of mechanical force to the power device in a direction tending to cause more outflow of uid than inow thereof.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, wherein:

Figure 1 is a fragmentary phantom perspective showing the application of the improved power unit to window lifters.

Figure 2 is a side elevation partly in section of the improved power unit.

Figure 3 is a top plan view of the power unit shown in Figure 2.

Figure 4 is a bottom plan view of the power unit.

Figure 5 is a section on the line 5 5, Figure 3.

Figures 6, 7, and 8 are fragmentary sectional views showing valve positions under diierent operating conditions.

Figure 9 is a fragmentary sectional view similar to Figures 5 8, showing a modied valve construction.

Figure 10 is a flow diagram of the system.

Referring now to the drawings, in Figure 1 there is illustrated a portion of an automobile l0 having a door l2 and a body structure I4. in the door l2 there is provided a window I6 adapted to be raised and lowered vertically. Rearwardly of the vehicle there is a window section I8 including a frame which is pivoted as indicated at 22 for rocking movement to open and close the window section I8.

The window it is provided with suitable guide means for controlling its vertical movement and is operatively connected to the power unit indicated generally at 2li, by a lever 2S connected to the piston rod 28 of the power unit, the lever 26 being pivoted at one end to a bracket 30 and having a pin 32 at its other end slidable longitudinally in the slot 34 of bracket 35 carried by the window frame. The power unit 2li is pivotally supported by a bracket Si suitably secured within the door cavity. The rear window section IB is moved by a similar power unit 24, the piston rod 28 of the power unit being connected to a lever 38 pivoted to the body of the vehicle as indicated at l0 and having a pin l2 at its other end slidable in a slot 46 provided in the bracket 4E carried by the window. In this case the power unit 2li is pivotally supported on a bracket 4l mounted within the frame of the vehicle below the rear window i 8.

In power units controlling the movement of windows of this type it is highly desirable to provide automatically operable locking means which prevent the windows being mechanically opened while the power unit is de-energized. At the same time, it is desirable to include means insuring that dangerous forces will not be applied to the windows in the event that an occupant of the vehicle interposes a hand or other part of his body between the window and the door or body frame. These two requirements are taken care o1 by the present construction as will subsequently be described.

Referring now to Figures 25, the power unit 2t comprises a unitary base 50 in the form of a casting. The base 50 is somewhat elongated and at one end is provided with a recessed cylindrical seat t2 for the reception of an electric motor Si. At the opposite side of the base 50 and at the same end as the motor 50, there is provided a cylindrical recess 5t adapted to receive a pump 5'! consisting of an internal gear 58 and an external gear 60. In practice, the internal gear is provided with one or more tooth than is provided on the external gear or pinion 50. The pump housing which is formed in part by the cylindrical recess 5t is closed at the lower side by a removable plate t! secured in place by clamping screws t2. Gear elements 5t and 60 are rotated by the motor and for this purpose the motor shaft 63 extends through an opening provided through the base 5B from the motor seat 52 to the recess 55.

At the opposite end of the base 5b there is provided a cylinder seat te surrounded by an annular seating nange 65. The cylinder seat til and flange G6 together serve as a closure for the otherwise open end of the power cylinder Gil and also serve to mount the cylinder' in operative position. Outwardly of the annular flange 65 is a cylindrical groove 'it in which is received a ring 'i2 bolted or otherwise secured in place as by the bolts lli. As indicated in Figure 2, the lower end of the cylinder @8 includes an outwardly extending radial iiange 'i6 engaged beneath the clamping ring 'i2 and of course, suitable sealing means are provided.

At the same end of the base 5t and at the side thereof opposite to the cylinder 68, there is provided a pivot support 'I8 having a transverse opening Ell therethrough and strengthened by supporting webs 52.` It will be observed that the axis of the opening Si! is perpendicular to and intersects the axis of the cylinder 53, so that the power unit as an assembly will in use rock about an axis intersecting the axis of the cylinder. Located within the cylinder 68 is a piston Se provided with a piston rod 2S which extends through the cylinder head Sli at the upper end of the cylinder.

Formed within the body of the base 5s and in communication with the bottom i the recess 56 are a pair of ports 9e and 92 in communication with opposite sides of the pump. The pump is designed to be run in opposite direction resulting in a reverse flow of huid therethrough and for this purpose the motor e is also reversible. In communication with the port $6 and within the body of the base 59 is a flow passage et which is closed at its outer end by a plug eli. Communicating with the passage 84 is another passage 98 which as best seen in Figure 2, extends through the cylinder seat Eli and thus aords communication between the lower end of the cylinder t8 and the pump port 9s. A second longitudinally extending passage Hi8 is provided within the body of the base 5G connected to port S2 and extends to one end of the base where it receives a iitting H32. The head 8S of the cylinder 53 carries a second fitting ld and the fittings are interconnected by a metal tube or conduit E06, thus aording communication between the upper end of the cylinder and the valve port SE.

Inasmuch as the power unit operates to raise and lower the windows of a vehicle, it is essential to insure that suicient force is not exerted on the window to cause injury to an occupant who catches 'his hand or other part of his body between the window and the frame or the door or vehicle. It is also desirable to permit the motor to run after full stroke of the piston. In the present ease this is taken care of by providing a small amount or clearance between one or both of the gear elements 58, Se and the closure plate Si. Thus, if the motor continues to run when the piston rod 86 is mechanically held against movement, there will be a circulation of iiuid within the pump between the ports 9B and 92. This now is insuiiicient to seriously decrease the eiiiciency of the pump in normal operation, but is suncient to limit the force with which the piston rod 28 is urged upwardly.

Inasmuch as the piston rod 28 occupies the portion of the cylinder ES above the piston 8&3, whereas no similar element is present in the portion of the cylinder beneath the piston, it will be apparent that a differential now of hydraulic fluid to and from the cylinder 6B takes place upon movement of the piston 84. Thus, when the piston 84 is moved upwardly by a flow of hydraulic iiuid under pressure into the lower end of the cylinder, more uid will flow into the lower end of the cylinder than is displaced from the upper end of the cylinder by movement of the piston therein. Conversely, as the piston moves downwardly there is a greater flow of hydraulic iiuid out of the lower end of the cylinder than inflow of fluid into the upper end of the cylinder.

This diirerential now requires a reservoir to accommodate the excess flow out of the cylinder upon movement of the piston in one direction and to supply the excess fluid required to move the cylinder in the opposite direction. In the present case the reservoir is provided in the form of a cavity H0 within the base 553. As best seen in Figure 3, where the outline of the cavity H0 appears in dotted lines, it will be observed that the reservoir is of a minimum width on the center line connecting the axis of the motor and the axis of the cylinder. At this point the width of the reservoir is determined by the space between the screw receiving bosses i Il which are also seen in Figure 5. At either side of this center line it is enlarged longitudinally of the base 63. The width of the reservoir on the adjacent center line appears directly in Figure 2 of the drawing. The reservoir lill is completed by a removable cover plate H2 provided with one or more removable nlling plugs H4.

As best seen in Figure 5 the hydraulic fluid flow passages Se and lll are interconnected by a transverse passage H6 which serves to connect two enlarged valve chambers H and $26. Between the chamber 22) and the passage HS is a cylindrical portion l2! whose diameter is intermediate that of the passage HS and the chamber iZ. The juncture between the transverse passage HS and the chamber H3 is formed to provide a valve seat 122. The juncture between the passage H6 and the cylindrical portion [El is formed to provide a valve seat H25. It will be observed that the now passages 94 and Hill connect directly with the enlarged chambers l E8 and l2!! respectively. Outer ends of the chambers H8 and i2@ are closed by removable plugs lZ and 28 respectively. A passage ISD connects an intermediate portion of the transverse passage il@ with the interior of the reservoir itil.

Located within the chamber l IS is a ball valve 32. Located within the cylindrical portion lil and partly within the chamber 52e is a ball valve 34. Intermediate the ball valves is a compression spring H38. The plugs |26 and t28 each include an inwardly extending projection 138 adapted to limit outward movement of the adjacent ball valve. The ball valve i3d is of a size to nt closely within the cylindrical sleeve portion 2| so as to have substantially uid-tight pistonlike movement therein. The spring 36 may be of a free length such that when hall valves 32 and i3d are in engagement with projections |38, the spring cannot contact both ball valves simultaneously. Alternatively, the spring may be of a free length such as to maintain both ball valves against the projections It` in the absence of iluid pressure. In any case however, when the ball valve 134 is moved by fluid pressure against its seat i24, the spring |36 will be compressed suniciently to apply a substantial force tending to hold the ball valve 132 in open position.

The arrangement described serves to cooperate with the power device for raising and lowering the window in a novel and valuable manner. Briefly, valves |32 and |34 operate as check valves during operation of the pump 51 in either direction, the valve in the pressure line closing to prevent iiuid from being forced into the reservoir and the valve in the suction line being open t permit flow of fluid from the reservoir to the suction line or vice versa depending upon the differential flow to and from the power cylinder ii. However, forces applied to the window in a direction tending to open the window create a uid block in the system which serves to lock the window in closed position when the pump is not operating. However, the window may be moved from open to closed position manually when the pump is not operating, due to by-pass iiow of fluid through the pump, as will subsequently appear.

When the pump l is operated in a direction to lower or open the window from its raised or closed position the valves |32 and |34 assume the position illustrated in Figure 6. At this time operation of the pump establishes pressure in the passage |063 thus forcing the valve I3@ to enter the cylinder |2| and to move therein in pistonlike movement until it seats against valve seat |24. Fluid under pressure from the pump enters the top of the cylinder 63 above the piston 84. This results in downward motion of the piston Si! in the cylinder and displaces a larger quantity of uid into passage 9d than is flowing into the cylinder through passage ltd. At this time valve |313, which is held on its seat under substantial hydraulic pressure, compresses the spring i355 "u relatively strongly and thus holds the valve |32 oi its seat |22. The excess hydraulic uid displaced from the cylinder as aforesaid, flows past ball valve |32 into passage ||6 and thence through passage |30 into the reservoir.

When the pump is operated in a direction to move the window from its lower or open position to its upper or closed position, the valves assume the position indicated in Figure '7. At this time the pump is discharging hydraulic uid ,i

under pressure into the passage 915 and thence through the passage 98 into the bottom of the cylinder BB beneath its piston 84. The pressure established in the passage 94 immediately closes valve |32 and at this time closing movement of the valve |32 is unopposed since negative pressure exists in the passage Iil. This is due to the differential displacement, more fluid flowing into the bottom of the cylinder 68 than is displaced from the top thereof, due to the presence of the piston rod 2B therein. Since more fiuid is required to raise the piston in the cylinder than is displaced from the cylinder to the pump, excess iuid is required in the operating system and this fluid ows from the reservoir ||0 past ball valve |34. At this time ball valve |315 is moved out of the cylinder portion |2| as seen in Figure 7.

If the window is in its lower or open position and if it is desired to raise the window manually (as may be the case if power fails or the motor is inoperative) the window is manually urged to the upward position thus applying an upward force on the piston Sli. This creates pressure in the cylinder above the piston and establishes positive pressure in passage |98, at the same time as a negative pressure is established in the passage Sill. Ball valve |36 immediately enters its cylinder portion |2| and may be forced against valve seat |24 if the pressure is sucient. Fluid under pressure in passage |00 passes 6? through the by-pass provided in the pumpv 51 and enters passage 94 whence it ows through passage Si to the bottom of the cylinder i'. This permits a slow upward movement of the window at a rate controlled by the capacity of the bypass through the pump.

When the window is n upper or closed position and forces are applied directly to the window tending to open the window, a hydraulic block is established which effectively prevents ope ing movement of the window. Any downward force directly on the window which would be eiiective to move the window establishes pressure beneath the piston 84. At this time valve |32 closes instantly since its closing movement is not opposed by spring action. The continuation of pressure on the window causes by-pass flow through the pump. Since the hydraulic system is completely iilled with fluid at all times, pre sure immediately builds up in passage it@ and chamber ld, thus moving valve i3d into its cylinder portion |2|. This takes place instantly and requires only a very small pressure in valve chamber |25, since this initial movement of valve i3d is not opposed by spring pressure. If the application of force to the window is continued and increased, pressure in the system builds up and when the pressure reaches a certain value, ball valve i3d will actually seat on valve seat E25. However, iiow of iiuid past the ball valve is ei ectively prevented at all times and accordingly, a fluid block is created which prevents downward movement oi the window. The conditions existing when a relatively small force is applied tending to open the window is illustrated in Figure 5, which shows ball valve |32 seated and ball valve lili having entered the cylinder ii. Ii excessive pressure is applied the only eiect is to move ball valve i3d onto its seat as illustrated in Figure 8. Ball valve |32 remains seated, since pressure in chamber i8 is at least as great as in chamber E25.

Referring now to Figure 9 there is illustrated an arrangement which is identical with that previously described except that valve 3242 has a larger effective area exposed to pressure with in 'the chamber i8 than is exposed by `ball valve i3d in chamber |29. This arrangement insures that with the ball valves in the position illustrated (which corresponds to a fluid block cone' dition in which relatively high pressure has been built up in the iiuid system) ball valve i3d will be the rst to unseat, thus maintaining ball valve Viau. on its seat if pressure is reduced. it will be appreciated that with ball valves of equal size illustrated in Figure 8, when pressure is reduced. to a value sufficient to permit the spring iii to cause the balls to separate, ball valve i3? may be the rst to unseat in which case rluid would iiow past the valve into the reservoir. While this cerdition is theoretically possible it would require very careful manipulation oi pressures on the window to eiiect any appreciable iow oi iiuid in the reservoir. However, with the construction illustrated in Figure 9 it is impossible tc opening movement of valve |3212', since with equai pressures in chambers HS and |29, valve i3d will move away from its seat before valve Hita. Movement of valve |34 away from its seat and along the cylinder |2| does not open the passages to flow but reduces pressure on the |35, thus permitting valve |32@ to remain on its seat under correspondingly reduced pressures within the chamber ||8.

Spring 36 may be of such length that when ball valve 132s is on its seat, valve i311 moves out of contact with the spring |36 before it emerges from the cylinder l2l. If this arrangement is employed it will be apparent that forces of any magnitude applied tending to open the window will immediately close the uid passages controlled by valves l32a. and 43A and this closure of these passages is maintained even though the pressure is built up to a very large value and thereafter reduced to a Very small value.

The drawings and the foregoing specification constitute a description of the improved power unit in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

l. A construction comprising a fluid passage, iirst and second outwardly facing valve seats at opposite ends of said passage, rst and second f valves movable respectively toward and away from said first and second seats, a cylinder eX- tending outwardly from said iirst seat in which said iirst valve is slidably received in duid-sealing relation for piston-like movement in said cylinder, an enlarged chamber beyond the end of said cylinder remote from said first seat, said rst valve being movable into said chamber to permit fluid flow past said iirst valve and through said iirst valve seat, and a compression spring in said passage engaging both of said valves when both of said valves are on their respective seats.

2. A construction as dened in claim l in which said spring` is of such length that it does not engage both valves when said rst valve is in said chamber.

3. A construction as defined in claim 1 in which said second valve is of larger eilective area than said first valve.

4. A construction as defined in claim 3 in which said spring is of such length that it does not engage both valves when said first valve is in said chamber.

5. A construction as donned in claim 1 in which said valves are balls.

6. A construction as dened in claim l comprising in addition a fluid reservoir, and a supply passage connecting said reservoir to said rst mentioned passage intermediate its ends.

7. l'n a hydraulic system comprising a pair of flow passages subjected alternately to pressure and suction, in normal operation, and which may be both subjected to pressure, a reservoir, rst and second supply passages connecting said reservoir respectively to said iiow passages, first and second check valves respectively in said first and second supply passages, said rst valve comprising a rst valve element, a cylinder in which said iirst valve element is movable, said cylinder being dimensioned to t said rst valve element in sealing relation, a valve seat at one end of said cylinder, and an enlarged chamber at the other end of said cylinder into which said rst valve element is movable to provide for flow of uid past said rst valve element and means Operatively connecting said valves eiective to establish a strong force holding said second valve open when said nrst valve element is seated, and effective to permit movement of the first valve element under low pressure in its ow line to a position in said cylinder preventing flow past said first valve element when the said second valve is closed.

8. Structure as defined in claim 7 in which said second valve comprises a second valve element and said means is interposed directly between said valve elements.

9. Structure as dened in claim 8 in which said means is a compression spring.

l0. A power regulator for opening and closing a movable closure, comprising a cylinder, a piston movable in said cylinder, a piston rod extending from one side of said piston, means for connecting said cylinder and piston rod to a closure in such relation that opening movement of the closure causes relative movement of said piston in said cylinder ni a direction away from said piston rod, a reversible pump, a nrst flow passage connecting one side of said pump to the end of said cylinder containing said piston rod, a second flow passage connecting the other side of said pump to the end of said cylinder remote from said piston rod, a restricted by-pass between opposite sides of said pump, a reservoir for containing iuid to compensate for differential iiow to and from said cylinder, a iirst supply passage connecting said reservoir and said rst flow passage, a second supply passage connecting said reservoir and said second dow passage, a rst check valve in said iirst supply passage, a second check valve in said second supply passage, said check valves comprising valve elements freely movable to open position when negative pressure is developed in the adjacent flow line, and spring means interposed directly between said valve elements operable by movement of said rst check valve element to closed position in response to high pressure in said iirst iiotv passage to hold said second check valve element in open position against any pressure in said second passage lower than the pressure in said iirst passage, said spring means permitting movement of said rst check valve element to position to prevent now of fluid therepast under any positive pressure in said irst passage when said second check valve element is closed by any positive pressure in said second passage.

11. Structure as dened in claim 10 in Which said iirst valve includes a cylinder in which its valve element is slidable therein in duid-sealing relation for piston-like movement, and said spring means is engageable with both of said valve elements.

l2. Structure as defined in claim 11 in which said second valve element has a larger effective area than said nrst valve element. i3. Structure as defined in claim 10 in which said closure is a window of a motor vehicle.

14. In a motor vehicle, a movable window, a piston and cylinder power device for raising and lowering said window, said power device including a piston rod at one side only of said piston, movement of said window toward open position being accompanied by movement of said piston in said cylinder in a direction away from said piston rod, duid flow passages connected to opposite ends of said cylinder, a restricted by-pass connecting said iiow passages, a reservoir, supply passages connecting said reservoir to said iiow passages, check valves in said supply passages including movable valve elements and means operably connecting said valve elements to provide for power movement of the window in either direction by the application of fluid under pressure to one or the other of said flow passages, to provide for 'manual closing of the window, and to establish a duid block. preventing manual opening of the window by the application of a force of any value directly to the window.

15. A hydraulic system comprising a reversible 9 pump, a cylinder, a piston in said cylinder, a piston rod connected to said piston at one side thereof, a first iiow passage connecting one side of said pump to the end of said cylinder containing said piston rod, a second flow passage connecting the other side of said pump to the other end of said cylinder, a restricted by-pass connecting opposite sides of said pump, a uid reservoir to compensate for differential fiow to and from said cylinder, first and second supply passages connecting said reservoir respectively to said first and second now passages, first and second check valves and seats respectively in said first and second supply passages, said check valves being adapted to be closed by pressure in the respective liow passages, said first check valve seat having a valve cylinder extending outwardly from the valve seat, an enlarged chamber into which said Valve cylinder opens, said first check valve being slidable in fluid-sealing relation in said valve cylinder and movable between a position on said valve seat and a position at least partly in said chamber to provide for ilow of fluid past said first check Valve, and a compression spring interposed between said iirst and second check valves.

16. A system as dened in claim 15 in which said spring is of such length that when said first check valve is in position at least partly in said chamber said spring exerts substantially no opening force on said second check valve.

17. A system as deiined in claim 15 in which said second check valve has a larger effective area exposed to pressure within the adjacent now passage than said first check valve.

1B. In combination with a closure member movable between closed and open positions, a hydraulic motor of the type having a differential inlet and outlet fluid flow, means connecting said motor to said closure member for direct power actuation of said closure in both opening and closing directions, a pump, iluid flow passages connecting opposite sides of said pump to opposite sides of said motor, means for reversing the direction of flow in said flow passages to reverse said motor, said motor being connected to said closure in such a way that inlet ilow to said motor through a iirst one of said flow passages is less than outlet ilow from said motor through the second one of said flow passages when said closure is being moved toward open position, a restricted bypass connecting said now passages, a fluid reservoir, iirst and second supply passages connecting said first and second :dow passages to said reservoir, first and second check valves each compri-sing a valve seat and valve member respectively located in said first and second supply passages, each of said check valves being adapted to close when pump pressure is directed into its corresponding flow passage, rst means responsive to establishment of pump pressure in said nrst iiow passage effective to establish a yieldable force tending to hold said second valve member open to permit excess uid flowing from the cutlet from said motor returning to said reservoir as said closure is moved toward open position, said first valve member being freely movable to open position when pump pressure is directed into said second flow passage to permit fluid to flow from said reservoir to said iirst fiow passage, and second means associated with said rst valve member to provide for closing of said iirst valve member despite prior closure of said second valve member under minimum bypass iiow conditions existing in said first iiow passage when force is 10 applied directly to said closure in opening direction while said pump is idle.

19. Structure as defined in claim 18 in which said valve seats are aligned and face outwardly from each other, and said first means comprises a compression spring interposed between said valve members.

20. Structure as defined in claim 19 in which said second means comprises a cylinder surrounding the seat of said first valve in which its valve member is slidable in sealing relation, an enlarged chamber spaced from said first valve seat and communicating with said rst flow passage into which said cylinder opens and into which said first valve member is at least partly movable to provide for iiow of fluid from said reservoir to said first flow passage.

21. Structure as defined in claim 20,-said spring being of such length that when said second valve member is seated, said first valve member does not engage said spring until it is in fluid sealing relation within said cylinder.

22. Structure as defined in claim 21, said second Valve member having a larger effective area exposed to the pressure of its associated flow passage than does said first valve member.

23. In apparatus of the character described, first and second valve seats, said first seat having a cylinder extending therefrom, a iirst valve member fitting closely within said cylinder and slidable therein in sealing relation between a position on said rst seat and a second position at least partly beyond the outer end of said cylinder to permit flow of fluid through said rst valve seat and past said first valve member, a second valve member associated with said second valve seat, means surrounding said second valve member and dening therewith a passage for the now of fluid through said second lvalve seat and past said second valve member whenever said second valve member is spaced from said second valve seat, and resilient means cooperable with said valve members effective to establish a resilient force urging said second valve member away from its seat when said first valve member is on its seat, and effective to urge said first valve member to but not beyond an intermediate sealing position in said cylinder when said second valve member is on its seat.

24. Structure as defined in claim 23 in which said valve seats are axially aligned in opposed relation, and said resilient means comprises a compression spring intermediate said valve members of a length to be partly compressed when both of said valve members are on their seats and fully extended when said second valve member is on its seat and said rst valve member is in intermediate sealing position in its cylinder.

25. In a motor vehicle, a movable window, a piston and cylinder power device for raising and lowering said window, said power device including a piston rod at one side only of said piston, movement of said window toward open position being accompanied by movement of said piston in said cylinder in a direction away from said piston rod, iiuid now passages connected to opposite ends of said cylinder, a restricted bypass connecting said flow passages, a reservoir, supply passages connecting said reservoir to said flow passages, check valves in said supply passages, each of said check valves being adapted to close when connected to the flow passage carrying iiuid under pressure to move said window in either direction, means operatively associated with both of said check valves for holding the proper one of said valves open to permit return of excess fluid to said reservoir under power movement of said window toward open position, and means operatively associated with the other of said valves to prevent flow of uid past said other valve under bypass iiow conditions when manual pressure is applied directly to said window in a direction to open it, thereby creating a iiuid block which prevents manual opening of the window.

26. In a motor vehicle, a movable window, a closed hydraulic system for actuating said window comprising a differential flow motor connected directly to said window for positive power actuation thereof in both directions, said motor arranged to require an excess of outlet ilow over inlet flow when operating in a direction to open said window, a reservoir connected to said system to supply excess fluid to said system when said motor is operated in a direction to close said window and to receive excess uid from said system when said motor is operated in a direction to open said window, check valves controlling flow of uid from said system to said reservoir, means operatively associated with said check valves effective to prevent return of fluid from said system to said reservoir when manual pressure is applied directly to said window tending to open said window, and means operatively associated with said check valves effective to provide for iow of uid from said system to said reservoir when said motor is supplied with fluid under pressure in a direction to open said window, whereby said window may be actuated in either direction by said motor, but a hydraulic block prevents opening of said window when said motor is not supplied with iiuid under pressure.

27. In a iiuid system, a pair of opposed valve seats, a cylinder extending outwardly from one valve seat, a laterally enlarged chamber at the outer end of said cylinder, a valve member movable toward and away from each of said seats, one of said valve members being movable in duid-sealing relation in said cylinder, and a compression spring interposed between said valve members, whereby said one valve member is movable in said cylinder to prevent flow of uid therepast while exerting a Variable valve lifting force on said other valve member.

28. In a fluid system, a pair of opposed valve seats, a cylinder extending outwardly from one valve seat, a laterally enlarged chamber at the outer end of said cylinder, a valve member movable toward and away from each of said seats, one of said valve members being movable 1n fluid-sealing relation in said cylinder, and means interposed directly between said valve members of a length such that closure of said other valve member permits entry of said one valve member into said cylinder in sealing relation therewith under minimum pressure conditions acting to move said one valve toward its seat, and such that movement of said one valve member towards its seat under a higher pressure condition establishes forces tending to unseat said other valve member.

29. Structure as defined in claim 28 in which said other valve member has a larger effective cross-sectional area exposed to fluid in the system than said one valve member, whereby said other Valve member is retained on its seat until the pressure acting on said one valve member exceeds the pressure acting on said other valve member.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 776,061 Hewitt Nov. 29, 1904 1,307,839 Williams June 24, 1919 1,409,116 Sammis Mar. 7, 1922 1,812,587 Ellis June 30, 1931 1,931,637 Wahl Oct. 24, 1933 1,999,693 Hill Apr, 30, 1935 2,122,045 Rose et al. June 28, 1938 2,282,977 Mast May 12, 1942 2,301,576 Parsons et al Nov. 10, 1942 2,388,755 McLeod Nov. 13, 1945 2,412,428 Rockwell Dec. 10, 1946 2,437,115 Muller et al Mar. 2, 1948 2,475,304 Bariiii July 5, 1949 FOREIGN PATENTS Number Country Date 781 Great Britain 1898 344,897 Italy Nov. 30, 1936 

